1. The invention relates to the controlled mixing of one fluid stream with another fluid stream particularly to the dispersion of small quantities of water in fuel oil streams to enhance efficiency in combustion.
2. It is found that by introducing small quantities of water into fuel oil, such as API grades No. 2, 4 and 6, the combustion of atomized streams of the oils is enhanced. Increases in combustion efficiency are obtained. Fuel oil and water are not miscible as is well known, and to produce the desired effect the water droplets must be uniformly and finely dispersed within the fuel oil stream. It is a problem to accomplish this, especially since in most large combustion systems the fuel oil stream and water stream parameters may vary significantly with time.
Generally, the approach which has been taken is a semibatch method which necessitates a storage reservoir. Oil at a constant pressure and at a flow rate which exceeds the maximum firing rate of the combustor is pumped into a reservoir. Under these constant conditions water is relatively easily and uniformly injected. Withdrawal from the reservoir of the oil-water mixture is accomplished by a separate pumping system, with the flow rate varying with time according to the desired firing rate of the combustor. The oil and water flowing into the reservoir are alternately turned full on or full off as the minimum and maximum levels in the reservoir dictate.
Of course many devices for mixing liquids in general and immiscible liquids in particular are known in the chemical process industry. However, much of such equipment is ill-suited for installation in the field environments where large industrial and marine combustion systems are found. For such applications the apparatus must be relatively compact, require modest power, be easily installed, reliable and easy to operate. Furthermore, many of the prior art systems simply proportion or meter a first liquid based on the pressure or flow of a second liquid. However, in combustion systems changes in both flow rate and pressure over a fairly wide range must be accomodated.
Of significance in the prior art, Junkins U.S. Pat. No. 2,337,851 discloses a proportioning system usable in the generation of steam. A flow of water through a first chamber in a valve mechanically activates an element, which through a linkage proportions the flow of water vapor in a second chamber. Lindsay in U.S. Pat. No. 3,647,002 discloses a demand proportioning valve for introducing relatively small quantities of an additive into a water stream for fire fighting equipment. The movement of a spring biased element within the main water stream mechanically changes the position of a like element located in the second stream.
Neither of these devices is entirely suited in performance and simplicity for use on fuel oil and water mixing. The stability of combustion and the efficiency benefits of water inclusion are dependent on uniformity of the product being atomized in the combustor. Small perturbations in streamline proportions which might be acceptable in other installations cannot be tolerated. Further there are safety aspects not present in many other situations. Under all operating and non-operations conditions, the flow of fuel oil into the water system must be prevented, to avoid contamination and fouling of the water system. Likewise, introduction of water into the fuel oil system must be prevented, particularly where there is no fuel oil flow. Accordingly, there is a need for an improved apparatus for mixing water with fuel oil and other like ingredients.